1. Field of the Invention
The present invention relates to a laser diode used in a light source for optical disks, optical communications or displays.
2. Description of the Related Art
In recent years, write-once DVD (Digital Versatile Disk) drives have rapidly become widespread. For reading and writing by the DVD drives, a red semiconductor LD (Laser Diode) in which an AlGaInP-based semiconductor is laminated on a GaAs substrate is used. For example, as shown in FIG. 11, a red semiconductor LD 100 has a configuration in which a lower cladding layer 111 made of AlInP, a lower guide layer 112 made of AlGaInP, an active layer 113 made of GaInP, an upper guide layer 114 made of AlGaInP, an upper cladding layer 115 made of AlInP and a contact layer 116 are laminated in this order on a GaAs substrate 110, and includes an upper electrode 117 on the contact layer 116 and a lower electrode 118 on the back surface of the GaAs substrate 110 (for example, refer to Japanese Unexamined Patent Application Publication No. H5-21894). In the red semiconductor LD 100 with such a configuration, when a voltage is applied between the upper electrode 117 and the lower electrode 118, for example, electrons and holes are injected into the active layer 113 from the lower electrode 118 and the upper electrode 117, respectively. Then, the electrons and holes injected into the active layer 113 are recombined to generate (emit) photons.